1. Field of the Invention
The present invention is directed to a system for treatment of pathological tissue in a patient by charging a region containing the pathological tissue with heating radiation by means of a catheter.
2. Description of the Prior Art
It is known to treat pathological tissue by heating the pathological tissue, for example, with microwaves or ultrasound waves that are generated with suitable sources. To the extent that the resulting tissue temperatures lie below 45.degree. C., the cell metabolism is disturbed with the consequence that growth is slowed in the case of tumors or a regression of the tumor even occurs. This type of treatment is known as local hyperthermia. When temperatures above 45.degree. C. are reached, the cell protein coagulates, with the consequence that the tissue is necrotized. The latter type of treatment is referred to as thermotherapy.
In order to avoid the unintentional treatment of healthy tissue in the case of local hyperthermia and to avoid the unintentional necrotization of healthy tissue in the case of thermotherapy, suitable measures must be undertaken. In this context, U.S. Pat. No. 4,620,546 discloses that the region to be heated with a therapeutic ultrasound source be localized by detecting harmonics of the therapeutic ultrasound emitted by the therapeutic ultrasound source from the output signal of a diagnostic ultrasound transducer, and the position of the heated region identified on this basis is mixed into the ultrasound image. It is also known, for example from WO 91/13650, to bring a catheter into the region of the pathological tissue in a suitable way and to monitor the resulting temperatures with a temperature sensor integrated into the catheter. For protecting healthy tissue, moreover, the catheter can have a coolant flowing through it. Nonetheless, an unintentional treatment or necrotization of healthy tissue cannot be reliably precluded. In particular, the necrotization of healthy tissue can lead to a serious injury to the patient. In the treatment of benign prostate hyperplasia (BPH), for example, there is thus the risk of injury to one or both bladder sphincters. An injury to the outer sphincter (sphincter externus) leads to incontinence of the patient; injury to the inner sphincter (sphincter internus) deteriorates the procreative capability of the patient as a consequence of retrograde ejaculation.
A catheter is disclosed in U.S. Pat. No. 5,161,536 which is provided with an ultrasound transducer at its distal end. The ultrasound transducer responds to ultrasound incident thereon from an ultrasound diagnostic system, and generates output signals which are processed so that the position of the ultrasound transducer is mixed into the ultrasound image.